1. Technical Field
The present disclosure relates generally to a pneumatic tire for a vehicle and, more particularly, to a pneumatic tire for a vehicle that is capable of ensuring the uniform traction and stiffness of tread blocks through the application of three-dimensional (3D) kerfs for the optimization of stiffness to the tread blocks, thereby achieving excellent running performance on snowy, dry and wet roads.
2. Description of the Related Art
So far, various proposals have been made regarding pneumatic tires capable of improving running performance on a snowy road by enhancing the edge effect of the tires have been made. For example, a pneumatic tire in which kerfs are formed in a plurality of tread blocks extending in the circumferential and widthwise directions of the tire has been proposed.
However, in the conventional pneumatic tire, the kerfs are formed in the tread blocks and thus the tread blocks are separated by the kerfs, and thus the stiffness of the tread blocks is reduced, thereby causing the tread blocks to be easily deformed. Accordingly, a problem arises in that the kerfs collapse due to the deformation of the small blocks of the tread blocks separated by the kerfs during the rolling of the tire, the frictional force between the tire and a road is reduced, and then the leading portion of the tire is pushed into the inside of the tire, thereby reducing the running performance of a tire, particularly the control stability and acceleration and braking performance of the tire.
In order to improve such kerfs, a tire, including so-called three-dimensional (3D) kerfs formed by changing not only the shape thereof in a horizontal direction but also the shape thereof in a vertical direction into curved shapes, has been proposed. As conventional 3D kerf technologies, a technology for kerfs having two-pronged blades known as Y-shaped blades (see EP Patent publication No. EP0543267 B1), a technology for kerfs having blades configured such that various types of protrusions are formed on the sides of the blades (see EP Patent Publication No. EP1073562 B1), and a technology for kerfs having blades whose vertical sections are shaped in the form of straight lines and waveforms (see Japanese Patent Publication No. 2005-170308) have disclosed.
However, the problem of a reduction in the stiffness of tread blocks attributable to kerfs still needs to be overcome. Furthermore, in the case of stepped kerfs, a problem arises in that the blocks of stepped portions become thin and thus hang in tatters, thereby damaging the quality of the appearance of a tire.